1. Field of Invention
The present invention relates to an electro-optical device, such as an active matrix addressing liquid crystal device, an electrophoresis similar to an electronic paper, an EL (electro-luminescence) display device, and an electronic emission device (field emission display and surface-conduction electron-emitter display). Further, the present invention relates to an electronic apparatus including such an electro-optical device.
2. Description of Related Art
A related art electro-optical device, such as a so-called active matrix addressing liquid crystal display, is known which, for example, includes pixel electrodes arranged in a matrix, thin film transistors (hereinafter “TFT”) connected to each of the electrodes, and data lines and scanning lines connected to each of the TFTs and provided parallel to the row and column directions, respectively, on a substrate.
In addition to the above-mentioned configuration, such an electro-optical device may include, on the substrate, a variety of circuits, such as a precharge circuit, to apply an image signal suitably to a data line, a sampling circuit, a data line driving circuit, or a scanning line driving circuit to apply a scanning signal suitably to a scanning line. Such circuits are normally provided in the vicinity of an image displaying area, where pixel electrodes or TFTs are defined to be arranged in a matrix. Also, such circuits include circuit elements, such as a switching element, or wires, if necessary. In this way, the active matrix addressing is made possible by appropriately driving the data line or scanning line by a variety of circuits provided on the peripheral area.
However, the switching element composing such variety of circuits has the following problems. That is, a projection display having a liquid crystal display includes, in addition to the above-described various elements, a counter substrate disposed to face the substrate, and a liquid crystal layer disposed between the substrate and the counter substrate, a light component being transmitted from a relatively powerful light source to the liquid crystal display. In the event that projection light is illuminated from the counter substrate, the light is transmitted through the liquid crystal layer and the substrate, and finally projected on a screen, thereby configuring an image. However, the direction of light within a liquid crystal display is, in fact, not always regular. For instance, the light once emitted from the liquid crystal display may possibly be reflected on a variety of elements within a mounting case for accommodating the liquid crystal display, resulting in the light returning to the liquid crystal display. Also, there has been known a related art projection display capable of displaying color where, for example, three liquid crystal displays corresponding to red, green, and blue are disposed to face one another with a prism thereamong, two liquid crystal displays may be disposed to face each other with the prism therebetween. In this case, light emitted from one liquid crystal display is incident on the other liquid crystal display more directly from the direction opposite to the direction on which the projection light is originally incident.
If there exists such returned light, the returned light incident on the switching element may cause its operation to malfunction. That is, in the event that the switching element is a TFT including a semiconductor layer, the returned light may possible be incident on the semiconductor layer, especially in its channel region, and the semiconductor layer may be excited, generating a light leak current which may disturb the accurate control of conduction or non-conduction in the channel region.
In order to cope with the above-described problems, a technique such as that disclosed in Japanese Unexamined Patent Application Publication No. 11-194360 is related art. The electro-optical device of Japanese Unexamined Patent Application Publication No. 11-194360 includes a light shielding film in the lower side of the switching element. Owing to the light shielding film, even though returned light is incident from the direction opposite to the incidence direction of the projection light, the progress of light can be blocked before it reaches the switching element.
However, the above-described electro-optical device has the following problems. That is, since the above-mentioned configuration for providing a light shielding film below the switching element on the substrate has a laminated structure of the light shielding film, an interlayer insulating film thereon, a semiconductor layer of a TFT which is a switching element thereon, a gate insulating film, and a gate electrode film, a crack may be created in the interlayer insulating film and even in the semiconductor layer owing to the relationship between the gate electrode film and the light shielding film. Such phenomenon may cause the switching element to break. That is, a crack is created when the edges of the gate electrode film and the light shielding film are formed not to overlap each other in plan view, and it is most likely to be created especially when the edges of both of them are in the same line.